You can use the argument that diseases were reducing in occurence at the same time that vaccines were being introduced to the general population - though this was at the same time as major social reforms like clean drinking water, sewer systems, washing facilities, and healthier lifestyles. It was just the vaccines have major PR which convinces people that they work when in fact they have never been proven to work in humans.....

Unless you can point to the gold standard test of a double blind randomised trial....

J